HWS Vol. 2 gives a pretty good background and description of the Cal. .30 Blank Cartridge, T61 (Antenna Erecting) but it doesn’t say how it was used (except to say that it was used with the AN/CRN-1 Radio).

Phil, the T-2 AN/CRN-1 was a radio buoy which was dropped over sea for navigational purposes. To my understanding of such devices the antenna has to be errected after the device is out of the aircraft and in the water. So a “CAD” cartridge makes sense here. The systems I knew so far had spring loaded folding antennas or self errecting strip shaped antennas.